Adaptive microprocessor control system and method for providing multiple heating modes in twinned furnaces

Abstract

In a heating system containing twinned furnaces capable of independently operating at multiple levels, a method for providing multiple heating modes to satisfy a required heating load during a given cycle, there being some total number of heating modes, wherein each heating mode may be activated for a time interval whose length is a function of furnace activity during the most recent previous cycle. The method comprises the steps of: determining the existence of a heating load to be satisfied; operating both furnaces independently at levels appropriate to a first heating mode for a first time interval that does not exceed a first predetermined limit; for each subsequent heating mode up to a number of one less than the total number of heating modes, operating both furnaces independently at levels appropriate to each subsequent heating mode for a subsequent time interval that does not exceed a subsequent predetermined limit; and operating both furnaces independently at levels appropriate to a final heating mode for a final time interval until the heating load is satisfied; calculating a thermal load requirement, as a function of all of the time intervals; and predetermining all of the predetermined time intervals for a next cycle, from the calculated thermal load requirement.

What is claimed is: 
     
       1. In a heating system containing twinned furnaces capable of independently operating at multiple levels, a method for providing multiple heating modes to satisfy a required heating load during a given cycle, there being some total number of heating modes, wherein each heating mode may be activated for a time interval whose length is a function of furnace activity during a most recent previous cycle, comprising the steps of: determining an existence of a heating load to be satisfied;   operating both furnaces independently at levels appropriate to a first heating mode for a first time interval that does not exceed a first predetermined limit;   for each subsequent heating mode up to a number of one less than the total number of heating modes, operating both furnaces independently at levels appropriate to said subsequent heating mode for a subsequent time interval that does not exceed a subsequent predetermined limit; and   operating both furnaces independently at levels appropriate to a final heating mode for a final time interval until the heating load is satisfied;   calculating a thermal load requirement as a function of all of said time intervals; and   predetermining all of said predetermined time intervals for a next cycle from the calculated thermal load requirement.   
     
     
       2. The method of claim 1, further comprising the steps of: determining if the heating load is satisfied while both furnaces are operating for each given heating mode;   if the heating load is satisfied, terminating operation of said furnaces at a heating mode in which said heating load is satisfied; and   if the heating load is satisfied prior to the final heating mode, aborting initiation of operation of all heating modes subsequent to said heating mode during which said heating load is satisfied.   
     
     
       3. The method of claim 1 where determining the existence of a heating load to be satisfied is determined by monitoring a single-stage thermostat. 
     
     
       4. A method for providing a two stage heating cycle using twinned single stage furnaces, comprising a first and a second furnace, as a function of a most recent previous heating cycle comprising the steps of: determining the existence of a heating load to be satisfied;   running blowers in both said furnaces and burners in said first furnace only, for a first time interval that does not exceed a predetermined limit, said running of said blowers in both said furnaces and burners in said first furnace only comprising a first heating mode;   running the blowers and burners in both said furnaces for a second time interval until the heating load is satisfied, said running of said blowers and burners in both said furnaces comprising a second heating mode;   calculating a thermal load requirement, as a function of said first time interval and said second time interval; and   predetermining the first time interval limit, for a next cycle from the calculated thermal load requirement.   
     
     
       5. The method of claim 4, further comprising the steps of: determining if the heating load is satisfied while the furnaces are operating in said first heating mode;   if the heating load is satisfied, terminating the first heating mode; and   if the heating load is satisfied in the first heating mode, aborting initiation of second heating mode.   
     
     
       6. A method for providing three heating modes using twinned multi-stage furnaces, comprising a first and a second furnace, as a function of a most recent previous heating cycle comprising the steps of: determining an existence of a heating load to be satisfied;   running blowers in both said furnaces and burners in said first furnace only at low fire for a first time interval that does not exceed a first predetermined limit, said running of said blowers in both said furnaces and burners in said first furnace only at low fire comprising a first heating mode;   running the blowers and burners in both said furnaces at low fire for a second time interval that does not exceed a second predetermined limit, said running of said blowers and burners in both said furnaces at low fire comprising a second heating mode;   running the blowers and burners in both said furnaces at high fire for a final time interval until the heating load is satisfied, said running the blowers and burners in both said furnaces at high fire comprising a third heating mode;   calculating a thermal load requirement, as a function of all of said time intervals; and   predetermining all of said predetermined time intervals, for a next cycle from the calculated thermal load requirement.   
     
     
       7. The method of claim 6, further comprising the steps of: determining if the heating load is satisfied while each furnace is operating for each given heating mode;   if the heating load is satisfied, terminating operation of a heating mode in which said heating load is satisfied; and   if the heating load is satisfied prior to operation in the third heating mode, aborting initiation of operation all heating modes subsequent to said mode in which said heating load is satisfied.